This invention relates to a cannula used for vessel retraction, and more particularly to a cannula and method that includes an endoscopic retractor for vessel ligation.
Certain cannulas have surgical tools located within the cannula for performing surgical operations on a vessel of interest. The cannula is inserted into a surgical site with the distal end of the cannula positioned near the vessel of interest. An endoscope positioned within the cannula allows the surgeon to view the target area, and allows the surgeon to position the surgical tool correctly. One common procedure is to ligate a vessel or other tissue by tightening a suture loop tied as a slipknot on the vessel before transection to provide hemostasis to the vessel.
However, surgeons encounter several difficulties in ligation procedures. In one ligation procedure, a second incision must be made at the opposite end of the vessel of interest to ligate and transect the vessel. Multiple incisions are invasive and should be minimized if possible. In order to avoid this second incision, some conventional methods require tying a suture loop around the vessel, and pushing the loop along the vessel with a knot pusher until the opposite end is reached. Then, the loop is tightened to provide ligation. However, this procedure is difficult because the slipknot often catches on stumps of cut tributaries or other tissue, and then constricts around the vessel at the wrong position. Also, there is no easy method for transecting the vessel after the suture loop is tied to the vessel without potentially prematurely severing the suture.
Thus, a device and method is needed to allow remote, one-incision, ligation of a vessel which allows a suture loop to be moved reliably to the site of interest, and ensures that the transection instrument is able to transect the vessel, and cut the suture.
In accordance with the present invention, a retractor is positioned within a cannula with a dissection cradle end of the retractor positioned at the distal end of the cannula. The retractor includes a first portion that has an axis approximately parallel to a central axis of the cannula, and a second portion that has an axis which is at an angle with respect to the central axis of the cannula. The dissection cradle is located at the distal end of the second portion of the retractor. In another embodiment, the retractor includes two legs having substantially parallel axes that selectively protrude from the distal end of the cannula. The protruding legs support the dissection cradle formed in the shape or a loop that is positioned in a plane skewed relative to the axes of the legs, with a bottom of the loop directed away from the cannula. Thus, in operation, when the surgeon locates a vein and side branch of interest, the surgeon extends the retractor to cradle the vein in the dissection cradle. Once cradled, the retractor may be fully extended, pulling the vein away from the axis of the cannula causing the side branch to be isolated and exposed to a surgical tool. The surgical tool may then be extended from within the cannula to operate on the isolated and exposed side branch.
In another embodiment, the top of the loop of the dissection cradle is flat and thin, allowing atraumatic support of the vein, and minimizing contact between the retractor and the surgical tool. In yet a further embodiment, the retractor includes a single leg with the loop formed by the one leg of the retractor, and with a stopper coupled to the distal end of the retractor. In still another embodiment, the cannula comprises a sliding tube which encases the retractor, and in a first position is extended out to encase the second portion of the retractor, and in a second position is extended to encase only the first portion of the retractor. In response to being in the first position, the second and first portions of the retractor are both approximately parallel to the axis of the cannula. In the second position, the second portion of the retractor is skewed relative to the axis of the cannula.
In accordance with an alternate embodiment of the present invention, a retractor is positioned within a cannula with a dissection cradle end of the retractor positioned at the distal end of the cannula. The dissection cradle comprises a shoulder part and a curved channel part. Suture forming a suture loop is threaded through a hole in a tension mount that is fixed to the distal end of the cannula and is abutted against the distal end of the shoulder. Upon advancement to the surgical site of interest, the suture loop is safely maintained in place due to the tension provided by the tension mount and the support provided by the shoulder. The curved channel provides a groove in which the vessel of interest may be cradled. Upon retraction of the retractor, the suture loop is displaced onto the vessel at the desired position for ligation. In one embodiment, the loop is tightened by detaching the proximal end of the suture from the cannula and pulling on the suture, constricting the suture loop. In an alternate embodiment, a manual controller for retracting the retractor is attached to the proximal end of the suture. Upon slidable retraction of the manual controller, the retractor is retracted, the loop is displaced onto the vessel, and the loop is tightened.
In a further embodiment, a transecting device is positioned within the cannula. The distal end of the tension mount is positioned to allow the distal end to be proximal to the shoulder of the dissection cradle responsive to the shoulder being in an axial position relative to the tension mount. This results in the suture and vessel being reliably positioned within reach of the transecting device for transection of the vessel and cutting of the suture.
Finally, in a preferred embodiment, the retractor has a distal end having an axis skewed relative to the central axis of the cannula, thus facilitating accurate positioning of the vessel and suture for transection and cutting and ensuring the proper displacement of the suture loop onto the vessel in response to the retraction of the retractor.